Internal combustion engine manufacturers are constantly seeking to increase power output and fuel efficiency of their products. One method of generally increasing efficiency and power is to reduce the oscillating mass of an engine, e.g., of the pistons, connecting rods, and other moving parts of the engine. Efforts to increase engine power and/or efficiency also may also result in an increase in pressure and/or temperature within the combustion chamber during operation.
Engines, and in particular the pistons of the engine, are therefore under increased stress as a result of these reductions in weight and increased pressures and temperatures associated with engine operation. Piston cooling is therefore increasingly important for withstanding the increased stress of such operational conditions over the life of the engine.
To reduce the operating temperatures of piston components, a cooling gallery may be provided about a perimeter of the piston. A coolant such as crankcase oil may be introduced to the cooling gallery, and may be distributed about the cooling gallery by the reciprocating motion of the piston, thereby reducing the operating temperature of the piston. At the same time, the cooling galleries may increase overall complexity of the piston assembly and manufacturing of the same.
Known methodologies for securing piston components together may require certain compromises in the cooling gallery configuration. For example, friction welding creates relatively large weld curls which occupy space within the gallery and thereby reduce an overall volume of the cooling gallery. Laser welding may create weld spatter that adheres to interior surfaces of the cooling gallery, generally requiring additional cleanup or machining after the welding process is completed. Induction heating, while resulting in reduced material waste of the joined components such as weld curls or spatter, generally requires relatively large induction coils to be interposed between the piston components being joined. The delay required to allow removal of the coils from between the two components before they are brought into contact after heating necessarily results in a loss of at least some heat energy, thereby creating a need for additional energy to be introduced into the joint to adequately join the components.
Accordingly, there is a need for a piston and manufacturing process that addresses the above problems.